Electromagnetic wave energy converter

ABSTRACT

Electromagnetic wave energy is converted into electric power with an array of mutually insulated electromagnetic wave absorber elements each responsive to an electric field component of the wave as it impinges thereon. Each element includes a portion tapered in the direction of wave propagation to provide a relatively wideband response spectrum. Each element includes an output for deriving a voltage replica of the electric field variations intercepted by it. Adjacent elements are positioned relative to each other so that an electric field subsists between adjacent elements in response to the impinging wave. The electric field results in a voltage difference between adjacent elements that is fed to a rectifier to derive d.c. output power. The element pairs may be arranged in a two-dimensional array to provide power conversion of randomly polarized electromagnetic waves, such as sunlight.

Unite States Patent [1 1 Fletcher et al.

[ Sept. 18, 1973 ELECTROMAGNETIC WAVE ENERGY CONVERTER [76] Inventors:James C. Fletcher, Administrator of the National Aeronautics and SpaceAdministration with respect to an invention of; Robert L. Bailey,Gainesville, Fla.

[22] Filed: Sept. 27, 1972 1211' Appl. No.: 292,698

I [52] US. Cl 321/15, 136/89, 250/212 [51] Int. Cl 02m [58] Field ofSearch 136/89; 250/212;

[56] References Cited 0 UNITED STATES PATENTS 3,026,439 3/1962 Geer250/212 X 3,121,648 2/1964 Jensen 136/89 3,232,795 2/1966 Gillette etal.... 250/212 X 3,350,234 10/1967 Ule 250/212 X 3,427,200 2/1969 Lapinet al... 136/89 3,448,273 6/1969 Webb 250/212 X 3,615,853 10/1971 Paine136/89 Primary ExaminerWilliam M. Shoop, .lr.

Attorney-R. F. Kempf et al.

[57] ABSTRACT Electromagnetic wave energy is converted into electricpower with an array of mutually insulated electromagnetic wave absorberelements each responsive to an I electric field component of the wave asit impinges thereon. Each element includes a portion tapered in thedirection of wave propagation to provide a relatively wideband responsespectrum. Each element includes an output for deriving a voltage replicaof the electric field variations intercepted by it. Adjacent elementsare positioned relative to each other so that an electric field subsistsbetween adjacent elements in response to the impinging wave. Theelectric field results in a voltage difference between adjacent elementsthat is fed to a rectifier to derive d.c. output power. The elementpairs may be arranged in a two-dimensional array to provide powerconversion of randomly polarized electromagnetic waves, such assunlight.

19 Claims, 3 Drawing Figures I Patented Sept. 18, 1973 ELECTROMAGNETICWAVE ENERGY CONVERTER ORIGIN OF THE INVENTION The invention describedherein was made in the performance of work under a NASA contract and issubject to the provisions of Section 305 of the National Aeronautics andSpace Act of 1958, Public Law 85-568 (72 Stat. 435; 42 U.S.C. 2457).

FIELD OF INVENTION The present invention relates generally to devicesfor converting electromagnetic wave energy into electric power and, moreparticularly, to a device including a number of relatively closelyspaced electromagnetic wave absorber elements having tapered portionsresponsive to wide band electromagnetic wave radiation.

BACKGROUND OF THE INVENTION Devices for converting radiant energy intousable power have been considered extensively in the past. Presently,the most commonly utilized devices for convetting radiant energy intousable power are solar cells which are adapted to convert solar energydirectly into electricity for power generating purposes. Solar cellsgenerally include oppositely doped semiconductor junctions whichgenerate current in response to solar energy impinging thereon. Solarcells depend for their operation on quantum properties of light energyto pro vide charge separation and hence current flow in the junctionregion. To date, the maximum efficiency of solar cells in convertingsolar energy into electric energy is approximately 13 percent. Inaddition to the relatively low conversion efficiency of solar energyinto electric power, solar cells are very expensive, as well as fragile,and usually must be mounted on a rigid, preferably flat substrate. Therequirement for arigid, flat substrate frequently substantiallyincreases the combined cost of the solar cells and their supportingstructure; if the supporting structure is a spacecraft panel, problemsof folding the panel and maintaining it in a rigid condition in use areencountered.

BRIEF DESCRlPTlON or THE INVENTION In accordance with the presentinvention, the wave properties of electromagnetic energy are utilized toconvert wide band electromagnetic wave energy into usable electricpower. The wide band energy impinges on an array of tapered absorberelements mutually insulated'from each other. The length, base area, andseparation of the elements are such that relatively wide bandenergy canbe absorbed. To achieve. maximum conversion of wide band energy, eachelement has a length, in the direction of wave propagation, equal toseveral wavelengths of the longest wavelength energy to be converted.Adjacent elements have spaced, sloping converging sides to enablemaximum conversion of energy wavelengths in the spectrum to beconverted. A voltage replica of the electric field variations absorbedby each element is derived at an output of each element. The differencebetween the voltage variations derived from adjacent elements is derivedand supplied to a rectifier to provide the power conversion. To maximizethe voltage difference, bases of adjacent absorber elements are spacedfrom each other by less than one wave length and preferably less than awavelength, of the received energy. The close spacing, relatively longlength and tapered sides also enable the absorber elements to functioneffectively as absorbers and prevent substantial re-radiation andreflection of the energy impinging thereon because the wave radiation istrapped in the converging interstices between the abosrbing elements.

In a preferred embodiment, the absorbers are formed of metallicelements, such as copper or other suitable material; however, absorbersmay consist of dielectric elements which function to direct theelectromagnetic wave energy onto an electromagnetic waveenergy-toelectricvoltage converter that derives a voltage replica of thewave. energy.

The invention may be utilized in conjunction with converting wave energyfrom the microwave region through the visible light spectrum. If theinvention is utilized for wave lengths in the solar spectrum, it isideally suited for use as a solar energy-to-electric power converter. Insuch a configuration, the absorber elements and electric componentsutilized for converting the voltage wave replicas into electric powermight be formed utilizing integrated circuit type manufacturingprocesses.

If the device is utilized for absorbing plane polarized electromagneticwaves, adjacent elements in the direction .of the wave electric fieldare aligned with each other in pairs such that maximum electric fieldvariations are derived between them but adjacent elements at rightangles to the electric field are packed as close as possible to eachother without electric contact, to maximize the active absorber area. Ifthe electromagnetic wave radiation is circularly or randomly polarized,as in the case of solar energy, a two-dimensional array of elements isprovided. The elements of the twodimensional array are positioned inmutually orthogonal directions having aligned columns and rows, and theelements preferably have symmetrical bases, such as a square or circle.Voltage differences are derived between adjacent pairs in bothorthogonal directions to provide maximum conversion efficiency of thecircularly or randomly polarized wave energy.

Because the conversionprocessis in response to the wave properties ofthe impinging electromagnetic wave energy, rather than the quantumproperties of such waves, and because of the small number of lossmechanisms individually and collectively optimal, it is believedpossible to achieve conversion efficiencies considerably. greater thanexisting solar cell type devices. Amajor advantage of the presentinvention is the separation of the wave absorption means and theconversion means permitting each to be individually optimized for theincident wave electromagnetic power spectrum. Another major advantage isthat by suitable choice of geometry for the absorbing elementsthe devicecan be made to match the incidentradiation spectrum. There is no knownmeans of achieving this desirable result with present art solar cells.Another advantage of the present invention is that it does not utilizetemperature-sensitive active semiconductor elements, for the basicabsorption process; the only semiconductor components are passivediodes. A further advantage of the present invention is that thesubstrate on which the elements are mounted can be mechanicallyflexible, to substantially eliminate many of the problems inherent withprior art fragile solar cells mounted on rigid substrates.

It is, accordingly, an object of the present invention to provide a newand improved device for converting electromagnetic wave energy intoelectric power.

Another object of the invention is to provide a new and improved devicefor converting wide band electromagnetic wave energy into electric powerwith relatively high efficiency, utilizing the wave properties of theenergy.

An additional object of the invention is to provide a new and improveddevice for converting circularly or randomly polarized electromagneticwave energy into electric power in response to electric field gradients.

Afurther objet of the invention is to provide a rela-' tivelyinexpensive device for converting electromagnetic wave energy intoelectric power, which device is relatively temperature-insensitive andcan be mounted on a flexible substrate.

An additional object is to provide a new and improved integrated circuittype device for converting solar energy into electric power.

An additional object is to provide a new and improved means of matchingthe response of the device to the incident electromagnetic wavespectrum.

The above and still further objects, features and advantages of thepresent invention will become apparent upon consideration of thefollowing detailed description of several specific embodiments thereof,especially when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective viewschematically illustrating the principles of the present invention;

FIG. 2 is a perspective diagram illustrating an embodiment of theinvention particularly adapted for converting solar energy into electricpower; and

FIG. 3 is a side sectional view of the embodiment illustrated in FIG. 2,along the lines 33.

DETAILED DESCRIPTION OF THEDRAWING Reference is now made to FIG. 1 ofthe drawing wherein is illustrated a pair of mutually insulated,substantially identical, pyramidal or conical, aligned and relativelyclosely packed, preferably metallic, as copper or other suitablematerial, electromagnetic wave absorber elements 11 and 12 which areresponsive to plane polarized wide band electromagnetic wave energy thatis propagating in a direction indicated by arrow 14 and has an electricfield with a gradient in a direction indicated by arrow'lS. Elements 11and 12 are constructed so that the shapes of every cross sectionparallel to their bases 13 are similar; the crosssectional areasdecrease for increasing distances from the bases 13 of the elements.Each of elements 11 and 12 includes a co-planar base 13, which may haveany desired configuration, such as a rectangle, square or circle, thatlies in a plane at right angles to the direction of wave propagation andis parallel to the electric field gradient 15. Elements 11 and 12 have asubstantial height, L, or length in the direction of wave energypropagation, between their base 13 and apex 17. The height is generallyseveral (up to approximately seventy five) wave lengths of the longestwavelength of the incident electromagnetic energy. Elements 11 and 12include adjacent, tapered side surfaces 16 that converge toward base 13and are positioned relative to each other to intercept the electricfield and absorb energy over a wide band of the electromagnetic wave.The apex of absorber elements 11 and 12 may be truncated in which case Lis the length of the truncated absorber elements.

Voltage variations derived in elements 11 and 12 in response to theelectric field variations of the electromagnetic wave energy impingingon surfaces 16 are transduced or converted into an electric voltage atterminals 21 and 22 of the elements. The voltages at terminals 21 and 22are replicas of the electric field variations impinging on absorberelements 11 and 12, whereby the voltage difference between terminals 21and 22 is proportional to the electric field gradient established by theplane polarized wave between facing surfaces 16 of elements 11 and 12.

The centerline spacing between adjacent elements 11 and 12 is such thatfor the incident electromagnetic wave spectrum, maximum voltage between21 and 22 occurs. It is of the order of a wavelength or less of theincident electromagnetic energy. The present invention responds to thisvoltage difference as derived over the desired spectrum of the incidentwave energy, to convert the wave energy into electric power.

The voltage difference between terminals 21 and 22 is converted intouseful d.c. electric power by a rectifier 23 and a filter capacitor 24,the voltage across which is supplied to a suitable external load, suchas resistor 25. The cathode is connected between the anode of therectifier diode and terminal 22. It is to be understood that a full waverectifier can be employed and that the d.c. voltage developed acrossexternal load 25 .can be supplied to any suitable device, such as ad.c.-to-

a.c. power frequency device.

The breadth,B, and depth,D, of base 13 as well as the length, L, andspacing between the elements 11 and 12 enable the band width to whichthe elements 11 and 12 are responsive to be adjusted to provide optimummatching to the spectrum of the electromagnetic wave energy impinging onabsorber elements 11 and 12. Close spacing between adjacent elements 11and 12, in addition to enabling the electric field gradient to becoupled with the greatest voltage difference to terminals 21 and 22,enables the electric field to be effectively trapped in the converginginterstices between facing, adjacent elements 11 and 12. Trapping of theelectric field variations occurs because elements 11 and 12 areabsorptive to the electric electromagnetic wave energy, whereby theenergy is not reflected and re-radiated from the elements.

Because the device of FIG. 1 is responsive to a plane polarizedelectromagnetic wave, it is preferable for the depth, D, of each of theelements 11 and 12 to be relatively narrow, less than wave length, sothat adjacent elements (not shown) can be packed as closely as possibleto either side of elements 11 and 12 in the horizontal direction. Closepacking of the elements enables maximum conversion of theelectromagnetic wave energy into electric power over the entire area ofan array which may be fabricated out of a multiplicity of element pairsas illustrated in FIG. 1. It is to be noted that the device of FIG. 1 isresponsive most efficiently to electromagnetic waves polarized so thatthe E field is in a plane parallel or coplanar with the long dimensionof bases 13. If the electromagnetic wave polarization direction wererotated there would be no substantial electric field variation betweenthe adjacent elements 11 and 12 and there would be substantially zerovoltage developed between terminals 21 and 22 with a resulting zeroconversion of electromagnetic wave energy into electric power.

The power of the electromagnetic wave incident on absorber elements Illand I2 is the incident power density times the effective area of the twoelements and can thereby be stated approximately as: 2 (EXH) BD, where Fand Q are respectively the electric and magnetic fields of the waveenergy. The power indicated by the equation is available so that it canbe converted into electric power supplied to a load, except for lossesin elements 1 l and 12, rectification, and stray losses. The losses ofelements 11 and 12 are principally due to skin effect or di-electriclosses, while the rectifier losses are the series resistance of thediode and stray losses are of the capacitor, and supporting substratefor elements 11 and 12. Stray losses can be minimized by locatingelements 11 and 12 on a low loss dielectric substrate to minimize losscurrents between the abosrber terminals.

The maximum wavelength restriction (about 75). of the longest wavelengthof the received spectrum) is provided to enable the shortest wavelengthof the desired spectrum to be trapped between adjacent elements and toprovide a relatively large surface area for extracting power from it. Ifthe maximum wavelength restriction, which corresponds approximately withthe length of a cone in an eyeball of a mammal (about 75A of the longestwavelength of the received spectrum), is exceeded by the incidentelectromagnetic energy spectrum, then the voltage output betweenterminals 2l22 of the device decreases.

If the device of FIG. I is utilized to convert plane polarized microwaveelectromagnetic wave energy into electric power, the rectifier circuitcan be connected to the terminals by a coaxial cable having a centerconductor connected directly to terminal 21 and a shielded outerconductor, possibly with a conventional balun,

connected to terminal 22. In the alternative, the reeti fier circuit canbe connected to elements 11 and 12 by a wave guide excited by thevoltage difference between terminals 21 and 22 so that propagation inthe wave guide is in one of the transverse electric modes, such as TE Insuch a configuration, upper and lower conducting surfaces of arectangular waveguide, between which the electric field is developed,are respectively connected to terminals 21 and 22.

One microwave absorber actually constructed and tested in accordancewith the present invention ineludes a pair of sheet copper pyramidalelements 11 and 12 having a length (L) of 13.3 centimeters, a breadth(B) of 6.3 centimeters, and a depth (D) of 2.0 centimeters. Thisabsorber pair had a center frequency of approximately 475 Mhz and a passband between approximately 200 and 700 Mhz. Increasing the length of theabosrber elements, without any changes in the base dimensions, of thepyramid, lowered the pass band center frequency, as well asthe-upper andlower cut-off frequencies.

may be rigid. Each of elements 31 preferably has a symmetrical base andcross section parallel to the base, which may be either circular orsquare, to enable equal voltages to be derived between adjacent ones ofelements 31 in the two orthogonal directions in response to orthogonalelectric field components at the same 1 wavelength. Thereby, the totalarray power output of FIG. 2 is insensitive to the polarizationdirection of the energy impinging thereon and the array can respond tocircularly polarized, as well as randomly polarized electromagnetic waveenergy.

To convert the electromagnetic wave energy impinging on elements 31 intoelectric power, adjacent elements are interconnected with each other bya half wave rectifying network similar to that illustrated in FIG. ll.In particular, aligned vertical elements 31a, 31b, and 31c areinterconnected so that the anodes of rectifier diodes 33, connected toelements 31a and 31c (which are separated from each other by element31b) are connected directly to the elements, while the cathodes of therectifier diodes are connected to one electrode of different capacitors34, the other electrodes which have a common connection to element 31b.

Similarly, horizontally aligned elements 31a, 31d, and

31le are connected to rectifier circuits such that the center element ofthe triad has a common connection to a pair of capacitors 34 which areconnected to the cathodes of diodes 33, having anodes connected to beresponsive to the voltage replicas respectively derived by absorberelement pairs 31a-31ld and 3Ie-31d. D. C. voltages developed acrosscapacitors 34 are supplied to a matrix of load resistors 135, one ofwhich is connected across each of the capacitors.

Elements 31 of FIG. 2 are illustrated as frustoconical structures havingupper bases with considerably smaller areas than the bases of theelements that are secured to substrate 32. The frusto-conicalconfiguration is preferred in certain instances because sharp points, asillustrated in the pyramidal elements 11 and 12, FIG. 1, may have atendency to fracture.

To enable the structure illustrated in FIG. 2 to function as a devicefor converting solar electromagnetic wave energy, which has the majorityof its power in the spectrum from 0.3 to 1.1 microns, into dc power, theelement dimensions and inter-element spacing must be on the order of amicron, whereby integrated circuit techniques are preferably employed infabrication. To this end, a solar energy'converter in accordance withthe present invention may take the form illustrated by thecross-sectional view illustrated in FIG. 3 but not limited to thisembodiment. In FIG. 3, electrically conductive cones 31a, 31b, and 31cproject from surface 35 of substrate 32. Alternate ones of cones 31,such as cones 33a and 3110, are ohmically connected to a P- dopedregions 36 of substrate 32, which are formed on surface 33 of substrate32 in superposition with the bases of cones 31a and 31c. A junction isformed between P-doped regions 36 and N-doped regions 37 which areformed in substrate 32 beneath P-doped regions 36. Regions 36 and 37respectively correspond with the anode and cathode-of diodes 33connected to cones 311a and 310, FIG. 2. Annular, dielectric oxide films42 are formed on face 35 over the intersections between the otherwiseexposed portions of the junctions between regions 36 and 37. Oxide films42 cover the peripheries of P-doped regions 36 and the innercireumference of N-doped regions 37. On the portion of P-doped regions36 not covered by oxide films 42 and the inner radial portion of thefilms, metal elements 31a and 31c are placed. The bases of elements 31aand 31c are ohmically connected to P-doped regions 36. Annular, metalfilms 38 are formed on face 35 in superposition with the otherwiseexposed regions 37 to form ohmic contacts with the N-doped regions.Metal films 38 are electrically insulated from elements 31a and 31c bydielectric films 42 which are disposed between metal films and elements.Metal film 39 is formed on face 35 at the base of element 31b and iselectrically connected to the base. The areas 41 of substrate 32 betweenadjacent metal films 38 and 39 form dielectrics for capacitors 34,having electrodes comprised of the metal film portions 38 and 39. A d.c.load is connected between metal film portions 38 and 39 so that the filmportions form load terminals.

The structure of FIG. 3 is formed by diffusing P and N regions 36 and 37onto surface 35 of substrate 32, utilizing conventional integratedcircuit techniques. Regions 36 and 37 are diffused only onto the areasbeneath and slightly to the sides of where cones 31a and 31d are to belocated. Thereafter, annular oxide regions 42 are formed overtheexterior portion of P- doped' region 36 and over a slight segment of theinterior of N-doped region 37 on surface 35. After oxide regions 42 havebeen formed, thin metal film contacts 38 are vacuum vapor deposited onthe exposed portions of N regions 37. Simultaneously with the formationof contacts 38 thin, metal film, annular contact 39 is vacuum vapordeposited on surface 35 in theregion outside of cone 31b. After metalfilms 38 and 39 have been deposited, cones 31a, 31b, and 31d aresuitably attached.

While metal is believed preferable in most instances for the absorberelements, it is to be understood that dielectric elements can also beutilized as elements for directing electromagnetic wave radiation to anoptical to d.c. converter diode. The dielectric elements wouldpreferably have the same configuration and dimensions as indicated suprawhile the optical to d.c. converter diode may be of a type described byJavin in the IEEE Spectrum, October, 1971, page 91.

While there have been described and illustrated several specificembodiments of the invention, it will be clear that variations in thedetails of the embodiments specifically illustrated and described may bemade without departing from the true spirit and scope of the inventionas defined in the appended claims.

I claim:

1. A device for converting electromagnetic wave energy having anelectric field into electric power comprising a plurality of mutuallyinsulated electromagnetic wave absorber elements each responsive to theelectric field, adjacent ones of said elements converging toward eachother in the direction of the wave propagation, each element includingmeans for deriv ing a voltage replica of variations of the electricfield intercepted by the element, adjacent ones of said elements beingpositioned relative to each other so that an electric field subsistsbetween said adjacent elements, and means responsive to the voltagedifference between the derived voltage replicas between two adjacentelements,

2. The device of claim 1 wherein each of the absorber elements ismetallic.

3. The device of claim I where each of the absorber elements comprises ametallic surface and has a length in the direction of wave propagationseveral wavelengths of the impinging electromagnetic wave.

4. The device of claim 3 wherein the adjacent elements havesubstantially coplanar bases, and the spacing between the adjacentelements at the bases thereof is of the order of no more than awavelength of the electromagnetic energy.

5. The device of claim I wherein the adjacent elements havesubstantially coplanar bases, and the spacing between the adjacentelements at the bases thereof is of the order of no more than awavelength of the electromagnetic energy.

6. The device of claim 1 wherein the conversion means responsive to thevoltage difference includes means for rectifying the voltage differenceto derive a d.c. voltage.

7. A device for converting circularly polarized or randomly polarizedelectromagnetic wave energy having an electric field into electric powercomprising a twodimensional array of mutually insulated electromagneticwave absorber elements each responsive to a component of the electricfield, each elements converging toward each other in the direction ofpropagation of the wave and including means for deriving a voltagereplica of variations of the electric field intercepted by the element,adjacent ones of said elements being positioned relative to each otherso that an electric field subsists between said adjacent elements, andmeans responsive to the voltage difference between the voltage replicasderived between two adjacent elements, said pairs being spaced at rightangles to each other in the array.

8. The device of claim 7 wherein each of the absorber elements ismetallic.

9. The device of claim 7 where each of the absorber elements comprises ametallic surface and has a length in the direction of wave propagationseveral wavelengths of the electromagnetic wave.

10. The device of claim 9 wherein the adjacent elements havesubstantially co-planar bases and the spacing between the adjacentelements at the bases thereof of the order of one wavelength or less ofthe electromagnetic energy.

11. The device of claim 7 wherein the adjacent elements havesubstantially coplanar bases and the spacing between the adjacentelements at the bases thereof is of the order of one wavelength or lessof the electromagnetic energy.

12. A device for converting solar, randomly polarized electromagneticwave energy in the wave length band from approximately 0.3 to 1.1microns into electric power comprising a dielectric substrate having aface substantially at right angles to the'direction of propagation ofthe solar electromagnetic wave energy, a plurality of mutually insulatedelectromagnetic wave, metallic absorber elements mounted on said face,each of said elements including tapered portion extending away from theface in the direction of propagation of the wave energy, each of saidelements having a decreasing cross-sectional area as the distance fromthe face increases and a length in the direction of propagation of thewave several wavelengths of the shortest wavelength of the spectrum, anintegrated circuit diode in said substrate connected to be responsive towave energy intercepted by alternately spaced ones of said elements, ametallic film on said substrate ohmically connected to the remainingmetallic elements, whereby a capacitor is formed in the substratedielectric between adjacent ones of said metallic films.

13. The device of claim 12 wherein each of the ele ments includes a basewith a symmetrical geometry in contact with said face, each elementhaving a cross section parallel to the base similar to the base.

14. The device of claim 13 wherein said face has a square cross section.

15. The device of claim 13 wherein said face has a circular crosssection.

16. The device of claim 13 wherein each of said elements is a frustum.

17. The device of claim 12 wherein the spacing between adjacent ones ofsaid elements is of the order of one wavelength or less of the shortestwavelength of the spectrum.

18. The device of claim 12 wherein the several wavelengths are between1.25 and 75.

19. A device for converting solar, randomly polarized electromagneticwave energy in the wave length band from approximately 0.3 to 1.1microns into electric power comprising a dielectric substrate having aface substantially at right angles to the direction of propagation ofthe solar electromagnetic wave energy, a plurality of mutually insulatedelectromagnetic wave, metallic absorber elements mounted on said face,each of said elements. including a tapered portion extending away fromthe face in the direction of propagation of the wave energy, each ofsaid elements having a decreasing cross-sectional area as the distancefrom the face increases, adjacent ones of said elements being spacedfrom each other by a distance on the order of a wavelength 'or less ofsaid energy, an integrated circuit diode in said substrate connected tobe responsive to wave energy intercepted by alternately spaced ones ofsaid elements, a first metallic film on said substrate ohmicallyconnected to one electrode of each of said diodes, a second metallicfilm on said substrate ohmically connected to the remaining metallicelements, said first and second films including load terminals whereby acapacitor is formed in the substrate dielectricbetween adjacent ones ofsaid metallic films, and

said load terminals.

1. A device for converting electromagnetic wave energy having anelectric field into electric power comprising a plurality of mutuallyinsulated electromagnetic wave absorber elements each responsive to theelectric field, adjacent ones of said elements converging toward eachother in the direction of the wave propagation, each element includingmeans for deriving a voltage replica of variations of the electric fieldintercepted by the element, adjacent ones of said elements beingpositioned relative to each other so that an electric field subsistsbetween said adjacent elements, and means responsive to the voltagedifference between the derived voltage replicas between two adjacentelements.
 2. The device of claim 1 wherein each of the absorber elementsis metallic.
 3. The device of claim 1 where each of the absorberelements comprises a metallic surface and has a length in the directionof wave propagation several wavelengths of the impinging electromagneticwave.
 4. The device of claim 3 wherein the adjacent elements havesubstantially coplanar bases, and the spacing between the adjacentelements at the bases thereof is of the order of no more than awavelength of the electromagnetic energy.
 5. The device of claim 1wherein the adjacent elements have substantially coplanar bases, and thespacing between the adjacent elements at the bases thereof is of theorder of no more than a wavelength of the electromagnetic energy.
 6. Thedevice of claim 1 wherein the conversion means responsive to the voltagedifference includes means for rectifying the voltage difference toderive a d.c. voltage.
 7. A device for converting circularly polarizedor randomly polarized electromagnetic wave energy having an electricfield into electric power comprising a two-dimensional array of mutuallyinsulated electromagnetic wave absorber elements each responsive to acomponent of the electric field, each elements converging toward eachother in the direction of propagation of the wave and including meansfor deriving a voltage replica of variations of the electric fieldintercepted by the element, adjacent ones of said elements beingpositioned relative to each other so that an electric field subsistsbetween said adjacent elements, and means responsive to the voltagedifference between the voltage replicas derived between two adjacentelements, said pairs being spaced at right angles to each other in thearray.
 8. The device of claim 7 wherein each of the absorber elements ismetallic.
 9. The device of claim 7 where each of the absorber elementscomprises a metallic surface and has a length in the direction of wavepropagation several wavelengths of the electromagnetic wave.
 10. Thedevice of claim 9 wherein the adjacent elements have substantiallyco-planar bases and the spacing between the adjacent elements at thebases thereof of the order of one wavelength or less of theelectromagnetic energy.
 11. The device of claim 7 wherein the adjacenTelements have substantially coplanar bases and the spacing between theadjacent elements at the bases thereof is of the order of one wavelengthor less of the electromagnetic energy.
 12. A device for convertingsolar, randomly polarized electromagnetic wave energy in the wave lengthband from approximately 0.3 to 1.1 microns into electric powercomprising a dielectric substrate having a face substantially at rightangles to the direction of propagation of the solar electromagnetic waveenergy, a plurality of mutually insulated electromagnetic wave, metallicabsorber elements mounted on said face, each of said elements includingtapered portion extending away from the face in the direction ofpropagation of the wave energy, each of said elements having adecreasing cross-sectional area as the distance from the face increasesand a length in the direction of propagation of the wave severalwavelengths of the shortest wavelength of the spectrum, an integratedcircuit diode in said substrate connected to be responsive to waveenergy intercepted by alternately spaced ones of said elements, ametallic film on said substrate ohmically connected to the remainingmetallic elements, whereby a capacitor is formed in the substratedielectric between adjacent ones of said metallic films.
 13. The deviceof claim 12 wherein each of the elements includes a base with asymmetrical geometry in contact with said face, each element having across section parallel to the base similar to the base.
 14. The deviceof claim 13 wherein said face has a square cross section.
 15. The deviceof claim 13 wherein said face has a circular cross section.
 16. Thedevice of claim 13 wherein each of said elements is a frustum.
 17. Thedevice of claim 12 wherein the spacing between adjacent ones of saidelements is of the order of one wavelength or less of the shortestwavelength of the spectrum.
 18. The device of claim 12 wherein theseveral wavelengths are between 1.25 and
 75. 19. A device for convertingsolar, randomly polarized electromagnetic wave energy in the wave lengthband from approximately 0.3 to 1.1 microns into electric powercomprising a dielectric substrate having a face substantially at rightangles to the direction of propagation of the solar electromagnetic waveenergy, a plurality of mutually insulated electromagnetic wave, metallicabsorber elements mounted on said face, each of said elements includinga tapered portion extending away from the face in the direction ofpropagation of the wave energy, each of said elements having adecreasing cross-sectional area as the distance from the face increases,adjacent ones of said elements being spaced from each other by adistance on the order of a wavelength or less of said energy, anintegrated circuit diode in said substrate connected to be responsive towave energy intercepted by alternately spaced ones of said elements, afirst metallic film on said substrate ohmically connected to oneelectrode of each of said diodes, a second metallic film on saidsubstrate ohmically connected to the remaining metallic elements, saidfirst and second films including load terminals whereby a capacitor isformed in the substrate dielectric between adjacent ones of saidmetallic films, and said load terminals.